It is known to provide spring-loaded mechanical assemblies with a metal coil spring having fabricated end details attached to the spring fro securing the spring within a system or assembly. Such spring assemblies can experience various problems, such as, for example, rust, noise from the spring coils contacting one another or contacting neighboring parts, metal fatigue through repeated cycles that diminish consistent spring rate performance and that eventually may lead to failure, dangerous sharp and hooked ends of the spring, etc.
Elastomeric springs or straps are used in place of metal springs in many different applications. For example, thermoplastic straps are used to support railroad air hoses, including at the point of connection between an air hose of one railroad car and an air hose of the adjacent railroad car connected thereto. Each railroad car has a strap connected between the railroad car and the fitting at the end of the air hose of the railroad car. When the fittings on the air hoses of adjacent cars are connected together, the elastomeric straps support the connection and must have sufficient strength to continue holding the fitting during a car disconnect procedure. Other uses for elastomeric straps that take advantage of the spring characteristics thereof include, but are not limited to supporting hoses on tractor-trailers, cargo containment straps, office chair tilt and tension members, machine counter balances such on dishwasher doors, etc.
It is known that elastomeric straps or springs develop memory when stretched over time or when stretched beyond an inherent limit thereof. When stretched beyond a yield point, the strap will not return to the pre-stretch length it possessed, but instead will be longer. Permanent de-formation in elastic members is known as “creep”. A thermoplastic strap of proper length and tension when new can become inadequate for its intended purpose when creep exceeds even a small amount.
It is well-known in the railroad industry that air hose support separations are one of the most common causes for undesired emergency braking. The costs associated with unplanned rail stoppages are significant since the train has to come to a complete stop, a train worker has to disembark the rail car and walk the length of the rail locating the failed strap, the strap has to be repaiers or replaced, then the brake line needs to be re-pressurized prior to resuming travel. Two root casues of air hose breakages are fastening clip breakage and strap breakage and/or strap elongation (yield). Due to the significant frequency of hose support failures, the Association of American Railroads (“AAR”) has revised the specification application to air hose support straps (AAR S-4006-03) to help improve the performance of hose supports.
Advantages can be obtained from a new construction and method to provide a thermoplastice spring that reduces the risk of breakage and elongation during use.